Ultrasonic-Assisted Extraction and Antioxidant Potential of Valuable Protein from Ulva rigida Macroalgae

Abstract

Ulva green macroalgae or sea lettuce are rich sources of protein with nutritional benefits that promote health as a future plant-based functional ingredient in the food industry. Alkaline pretreatment improved ultrasonic-assisted protein extraction from Ulva rigida biomass. Parameters affecting ultrasonic-assisted extraction of protein were type of solvent, biomass-solvent ratio, biomass preparation and extraction cycle. In vitro digestibility was evaluated from oven- and freeze-dried biomass. Results showed highest concentration and extraction yield of protein from U. rigida using alkaline rather than acid and distilled water. A high biomass–solvent ratio at 1:10 or 0.1 g mL−1 increased protein extraction. Higher alkaline concentration increased protein extraction. Highest protein extractability was 8.5% dry matter from freeze-dried U. rigida biomass, with highest protein extraction and antioxidant activity from extraction of U. rigida macroalgae at high alkaline concentrations. U. rigida macroalgae oven-dried biomass presented suitable human digestibility. Efficient pretreatment of U. rigida maximized protein hydrolysate and bioactive peptide production for wide-ranging applications.